Dye bleach process



United States Patent 3,414,411 DYE BLEACH PROCESS Stephen Michel and George M. Reitter, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N .Y., a corporation of New Jersey Filed Dec. 10, 1965, Ser. No. 512,907 17 (llaims. (Cl. 9629) This invention relates to photographic elements and processes and more particularly to photographic elements and processes for silver-dye-bleach systems.

The silver-dye-bleaclr system involves developing a silver image in an exposed silver halide emulsion containing bleachable dye, and bleaching the dye in just those areas where the silver has been developed. All of the silver ion is removed or rendered transparent and insensitive to light, leaving a dye-image in the areas where no metallic silver was present.

In all of the previously disclosed color photographic processes utilizing th above mentioned silver-dye-bleach system, it is necessary to subject the exposed film to a large number of processing baths. Although these multistep silver-dye-bleach processes yield acceptable color pictures, the large number of steps together with the long processing time required has prevented the utilization of such a process in an in-camera type system. We have found a new and improved method of utilizing the silver-dye-bleach process which retains the advantages of the prior art process, but eliminates the large number of processing steps and greatly reduces the time required to produce a color picture.

One object of this invention is to provide improved novel dye-bleach materials and processes. A further object of this invention is to provide novel dye-bleach materials and processes which allow short processing times. Another object of this invention is to provide novel dye-bleach materials and processes which can be utilized by a relatively unskilled individual. Another object of this invention is to provide novel dye bleach materials and processes suitable for in-camera processing. It is another object of this invention to provide novel photographic dye-bleach processes which reduce the number of processing baths or steps required to produce images by the dye-bleach system. Other objects of this invention will become apparent from the disclosure herein and the appended claims.

In one embodiment of this invention, dye images are produced in photographic elements comprising a support having thereon a silver halide emulsion containing the salt of an acid and a developed silver image having in association therewith a bleachable dye, or dye precursor by the method which comprises contacting the emulsion with a web having an acidic substituent which is capable of exchanging hydrogen ion with the cation of the salt of an acid which is present in the emulsion or activator to lower the pH of the emulsion to a level at which imagewise bleaching of the dye in areas of metallic silver and in the presence of a silver complexing agent may proceed. The dye bleaching is preferably conducted in the presence of a catalyst.

In another embodiment of this invention, a method is provided for producing dye images in an exposed silver halide emulsion having in association therewith a bleachable dye, which comprises elevating the pH of the emulsion, in the presence of a silver halide developer, to a level at which the developable silver halide is reduced to metallic silver. The element is then contacted with a web having an acidic substituent which exchanges hydrogen ion with the cation of the salt of a strong acid which is present in the emulsion or activator, thereby converting the said salt to its free acid form. Thus, the pH of the ice emulsion is lowered, stopping development and reducing the pH to a level at which bleaching of the dye occurs irnagewise in the presence of a silver complexing agent in areas where metallic silver is present. The bleaching is preferably conducted in the presence of dye bleach catalyst. A silver halide complexing agent is employed during processing to remove, or render light-insensitive, the silver ion. The use of such complexing agents permits the bleaching of the metallic silver to silver ion to be carried to completion.

In still another embodiment of this invention, a method of developing silver-dye-bleach elements is provided which requires only one processing solution and is suitable for in-camera processing. In this method, an exposed silver halide emulsion having in association therewith a bleachable dye or dye precursor is contacted in the presence of a silver halide developer, with an alkaline processing solution to elevate the pH to a level at which the developable silver halide is reduced to metallic silver, at least the alkaline processing solution being contained in a rupturable pod or container, e.g., a pressure rupturable container. In this process, suitable means are provided for rupturing the pod and evenly distributing the contents thereof over the exposed silver halide emulsion. The emulsion is contacted with a processing web having acid substituents. The processing web stops development by lowering the pH of the emulsion by ion exchange with the salt of an acid present in either the emulsion or the activator solution, or both. The salt of a strong acid is incorporated in the emulsion at any convenient time prior to contacting it with the acidic web, such as when the emulsion is made, or by incorporating the salt in the alkaline processing solution. The ion exchange lowers the pH to a level at which bleaching of the metallic silver and the dye in the presence of a silver complexing agent may be affected. In a variation of this embodiment, a timing layer may be coated over the acidic web. The rupturable pod may be affixed to the acid web or matrix and the exposed photographic element brought into contact with the pod and acidic web, the pod ruptured and the element and web contacted in overlying relationship with the contents of the pod evenly distributed between the web and the element. The timing layer serves to allow development to take place prior to reducing the pH by ion exchange between the acidic web and salt of a strong acid present in the alkaline processing solution or element.

In still another embodiment of the invention, an integral three-part photographic element is provided comprising as part 1, a light-sensitive material including a support having coated thereon at least one light-sensitive silver halide emulsion having in association therewith a bleachable dye. The light-sensitive element may contain a plurality of emulsions containing or having in contiguous colloid layers, different bleachable dyes to provide multicolor images. Part 2 comprises a rupturable pod containing an alkaline processing solution to raise the pH of the emul-, sion to a level at which, reduction of developable silver halide to metallic silver takes place when a silver halide developer is present. Part 3 of the photographic element comprises an acidic web which is capable of exchanging the hydrogen ion with the salt of a strong acid which is introduced into the emulsion at any convenient time prior to contacting the emulsion with the Web, the salt of a strong acid may be incorporated in the emulsion when it is made, or it may be added to the alkaline processing solution. The element of this invention may be assembled in various arrangements. For example, in a preferred embodiment the rupturable container is :aflixed to the processing web. Alternatively, the rupturable container may be attached to the light-sensitive element. If desired, all three parts may be included in a packet arrangement with the emulsion layer of part 1 facing the acidic web, and the rupturable container positioned between the lightsensitive element and the acidic processing web. If desired, parts 1 and 3 may be in the roll form, with part 2 being affixed to either part, preferably, part 3.

I This invention will be further illustrated in the accompanying drawing which shows a light-sensitive element, labeled part 1, comprising a support 1, overcoated with a blue-sensitive emulsion 2 which contains bleachable yellow dye, a green-sensitive emulsion 3 which contains a bleachable magenta dye and a red-sensitive emulsion 4 which contains a bleachable cyan dye. If desired, each of these emulsions may consist of two emulsions having different speeds and double coated to provide a wider latitude for the element. In some instances, it is desirable to provide between each emulsion layer a hydrophilic colloid interlayer which may contain various addenda, such as ballasted quinones (i.e., to prevent interlayer diffusion of reduced dye bleach catalyst), removable filter dyes, etc. The drawing further shows an acidic processing, web, labeled part 3, comprising a support 5 having coated thereon a hydrophilic colloid layer identified in the figure as gelatin containing acid containing free acid 6, and overcoated with a timing layer 7 identified in the figure as gelatin timing layer. A rupturable pod labeled part 2 is composed of a film 8 which may be ruptured by suitable means. The rupturable pod shown contains an alkaline processing material 9.

The light-sensitive emulsions employed in the elements and processes of this invention comprise any of the useful silver halide light-sensitive salts such as silver chloride, silver bromide, silver iodide, and mixed halide salts such as silver chlorobromide. The emulsions may be conventional surface sensitive emulsions, direct positive emulsions or internally sensitive emulsions. The emulsions used in this invention, as well as the photosensitive elements thereof, may be used to record light and other radiation, such as infrared, X-ray, etc. A wide variety of alkalipermeable binders may be used for the silver halide, such as gelatin, polyvinyl alcohol, water-soluble cellulose derivatives and other binders of the type referred to in column 13 of US. Patent No. 3,039,873. The emulsions may contain chemical sensitizers, spectral sensitizers, stabilizers, speed increasing compounds, gelatin plasticizers, and hardeners, examples of which are referred to in columns 10-12 of US. Patent 3,039,873.

Incorporated in the photographic elements used in this invention are bleachable dyes, preferably non-difiusible dyes, of the type well known in the art. The term bleachable dyes as used herein includes compounds which are dye precursors, i.e., compounds which become colored during processing of the photographic material. The term non-difiusible as used herein and in the appended claims refers to bleachable dyes which in themselves are nondiifusible in the emulsion, or dyes which are rendered nondiffusible by the use of a suitable mordant, such as those described in US. Patent No. 2,882,156. The elements of this invention may have a single emulsion coating for monochrome dye images formed from either one or a mixture of dyes, which dye images are either colored or neutral (e.g., black and White) images. Typical useful neutral dyes for such materials are the azo dyes described in British Patent 999,996. Also, the elements of the invention may have a plurality of coatings each containing a different bleachable dye for providing multi-color images. Especially useful arrangements are those in which at least three light-sensitive emulsion layers are provided which are respectively sensitized to blue, green and red radiation, and containing, respectively, non-diffusible yellow, magenta and cyan dyes. The emulsions used in this invention may contain the bleachable dyes. However, it is also possible, and sometimes preferable, to incorporate the bleachable dye in an alkali-permeable layer contiguous to the emulsion layer. This arrangement provides increased speed, especially when the bleachable dye containing layer is coated under the emulsion layer. Thus, in One useful arrangement a support has coated thereon, in the following order, layers containing, respectively, blue-sensitive silver halide; bleachable yellow dye; greensensitive silver halide; bleachable magenta dye; red-sensitive silver halide; and, bleachable cyan dye. Such an element would .be exposed through the support, As used herein and in the appended claims, the reference to bleachable dyes being in association with a particular layer means that the bleachable dye is in that layer or in an alkali-permeable layer contiguous to such layer.

Development of the exposed photographic emulsion is effected, in the presence of a silver halide developer, by elevating the pH of the emulsion with an alkaline processing solution. Advantageously, the pH of the emulsion is raised to about 9.0 or above. A wide variety of alkaline solutions can be employed, such as sodium or potassium hydroxide. Development rate controllers, such as potassium bromide, may be used. Other agents found in conventional developers, such as spreading agents (saponin), antifoggants and stabilizers may be included in the alkaline processing solution.

Conventional photographic developers are operable in the invention. These developers may be incorporated in emulsions in accordance with prior art procedures, or may be added to the alkaline processing solution referred to herein also as activator solution. In certain instances, it is possible to incorporate in the emulsion one molecule which contains both the developing function and the bleachable dye function. Such molecules are non-diffusible and the dye portion of the molecule must be bleachable.

In processing photographic elements in accordance with the invention, a suitable silver halide complexing agent is employed. As used herein and in the appended claims, the term complexing agent refers to compounds which either (1) dissolve and remove from the emulsion layer silver ion, or (2) stabilizing compounds which react with the silver ion to render itinsensitive to light and transparent. The complexing agents are incorporated in the activator solution or, in some instances, in the acidic processing web, or in both. Typical useful complexing agents are dimethylolthiourea, trimethylolthiourea, cyclic thione, 1-(5-hydroxyethyl)imidazolidene-Z-thione, etc.

Prior to contacting the developed silver halide emulsion with the acidic processing web in accordance withthe invention, the salt of a strong acid is introduced into the emulsion. The salt of an acid can be incorporated in the emulsion during the making thereof, or it may be incorporated in the alkaline processing solution, or in both. The salt of the strong acid reacts with the acidic processing web to reduce the pH of the emulsion at the proper time during processing; An ion exchange occurs between the acidic processing web and the salt of a strong acid,the strong acid salt losing its cation to the acidic function in the web, and thereby effectively lowering the pH of the emulsion to facilitate bleaching of the dye by the metallic silver in the presence of a silvercomplexing agent. Useful salts of strong acids in this invention are those which, in their free acid form, are capable of reducing the pH of the emulsion low enough to enable bleaching. Generally ,this is at a pH level of less than about 3, and preferably is less than about 2.0. Especially useful acids arethose which have an ionization constant greater than about l0 The salts of acids employed should be free from exerting deleterious effects on the photographic elements, such as fogging the emulsion, and they must not bleach the dyes in areas Where metallic silver is not present. Especially useful salts arethe ammonium (e.g., unsubstituted and substituted), alkali metal and alkaline earth chlorides, bromides, nitrates, sulfates, sulfonates, phosphates, phosphonates, and the like. Other useful acid salts include tetraalkyl ammonium chlorides, such as tetramethyl or tetrabutyl ammonium chloride, sodium chloride, sodium meta-t-but-yl-benzene sulfonate sodium salt suflicient to effectively lower the pH of the emulsion to a level at which bleaching of the dye takes place. Especially useful concentrations range from 0.5 to 2.0 moles of acid salt per liter of developer or activator. Of course, the concentration of the acid salt depends on the strength of the acid. There must be present a suflicient concentration of the acid, in the form of its salt, to reduce the pH to less than about 3.0 and preferably less than 2.0 or 1.5, When the ion exchange takes place.

The function of the acidic web employed in accordance with this invention is to stop development and activate bleaching. The acid web allows one-solution dye-bleach processing. The web itself may comprise any suitable support, such as paper, a polyolefin such as polyethylene or polypropylene; polycarbonate; or a cellulose ester such as cellulose acetate butyrate. When film supports are used, it is desirable to have a suitable subbing coating to adhere the acid to the web. If desired, the web itself may be a self-supporting acidic polymer, such as a cross-linked polystyrene having free acidic groups, such as sulfonic acid groups. Cation exchange membranes are also useful such as those described in Nature, volume 165, p. 568 (1950). It should be noted that it is unnecessary for the web to continue to be self-supporting after it is contacted with the emulsion, the important feature being that it should remain in contact with the emulsion for a sufiicient length of time to exchange hydrogen ion with the cation of the acid present in the emulsion.

The acidic processing web may comprise a suitable support, such as a film base of the type referred to above having a hydrophilic coating thereon containing a free acid which is capable of exchanging hydrogen ion with the cation of a strong acid salt present in the emulsion. A Wide variety of acids are suitable for this purpose, including strongly acidic polymers, ballasted sulfonic acids and ballasted phosphonic acids, such as dodecanesulfonic acid and hexadecanephosphonic acid. As employed herein the term ballasted refers to acids having limited mobility or complete immobility in aqueous media. Especially useful are the ballasted sulfonic acids, including high molecular weight monomeric acids such as an alpha-sulfostearic acid. Polymeric cation ion exchange resins may also be employed, such as phenol sulfonic acid condensed with formaldehyde or para-formaldehyde or polystyrene sulfonic acids. The acids may be adhered to the web in any convenient manner, preferably by incorporating the acid in an alkali permeable layer, such as a hydrophilic colloid, e.g., gelatin, polyvinyl alcohol and other colloids of the type referred to in column 13 of US Patent 3,039,873.

The processing web of the invention must contain suflicient free acid substituent to exchange hydrogen ion with the salt of a strong acid in the emulsion, and thereby reduce the pH of the emulsion to a level where bleaching of dye takes place. As noted above, silver halide complexing agents may be included in the acidic processing web, for example, by including the complexing agent with the free acid in an alkali permeable layer.

In preferred embodiments of the invention, the acidic processing web contains a colloid overcoating which serves as a timing layer. The purpose of this overcoating is to allow development of exposed silver halide to progress to completion prior to the exchange of hydrogen ion with the cation of the acid salt present in the emulsion. Gelatin, polyvinyl alcohol, and polyvinyl alcoholpolyvinyl acetate mixtures are the preferred colloidal timing substances, some examples of which are referred to in column 13 of US. Patent 3,039,873. Advantageously, the timing layer is coated at a concentration of at least 500 mg./ square foot, or about 0.5 mil in thickness. However, the concentration (or thickness) of the timing layer depends on several variables, such as strength of developer and pH, and thus may be varied considerably.

The light-sensitive emulsions employed in the process and elements of this invention may be coated on a wide variety of supports, including film bases such as polyethylene, terephthalate, cellulose acetate butyrate, polycarbonate, polyolefins (e.g., polyethylene and polypropylene) and the like. When such film bases are used, the photographic product obtained may be used, for example, as a transparency. If desired, the emulsions may be coated on an opaque support such as paper, polyolefin coated paper such as polyethylene or polypropylene coated paper which may be pigmented, with TiO for example, and electron bombarded to promote emulsion adhesion. When such supports are used, a color photographic print may be obtained. When the emulsions coated on such supports are exposed to an original, it is necessary to employ a suitable optical system to laterally reverse the image to have a right reading print.

Advantageously, the bleaching of the image dye is conducted in the presence of a suitable catalyst, such as a phenazine, a quinoxaline or an anthraquinone. A number of catalysts useful herein are described in US. Patents 2,183,395 and 2,270,118. In accordance with the invention, the catalyst may be incorporated in the emulsion, the alkaline processing material, the acidic processing web, or in more than one, or all of these elements. These compounds oxidize the metallic silver to silver ion, and in so doing are reduced. The reduced catalyst then cross-oxidizes with the image dye. This cross-oxidation decolorizes (i.e., bleaches) the image dye and oxidizes the catalyst back to its original state.

Compounds which are useful in oxidizing excess metallic silver to silver ion and which do not interact in their reduced form with the bleachable image dyes are known as silver bleaching agents; typical examples of which are oand m-nitrobenzene sulfonic acids, ditfusible azo dyes, etc. Other typical silver bleaching agents are disclosed in British Patent No. 533,190. These agents may be incorporated in the emulsion, the alkaline processing material, the acidic processing web, or in more than one, or in all, of these elements.

This invention will be further illustrated by the following examples.

EXAMPLE I A single layer silver chlorobromi de emulsion coating corresponding to the following structure was prepared:

Mg./ft. Silver chlorobromide (mg. of silver) 45 Photographic gelatin 400 Solantine Pink 4BL (CI 25380) 25 Poly-ot-methylallylaminoguanidine acetate 60 S-{OL [N,N bis(B hydroxyethyl)amino]methyl}-2- methylhydroquinone dimethyl sulfate 35 This coating was exposed through a 0.3 neutral density step tablet for one second at 18" with a No. 212 photoenlarger lamp, and dipped for three seconds in an activator solution having the composition:

Activator A NaOH g 3.5 2-hydroxy-3-aminophenazine g .6 Sodium chloride g Sodium m-nitrobenzene sulfonate g 25 Potassium bromide g 5 Water to 1 liter.

The coating was then squeegeed in contact with the dye acid sheet No. 1 (structure below) for 45 seconds, the sheets were separated and a positive dye image remained on the coating. All of the silver had been removed.

7 Acid sheet No. 1

The dye acid sheet used above is composed of a cellulose acetate film having a single layer coating thereon of the following composition:

Polyvinyl alcohol mg./ft. 560

a-Sulfostearic acid g./ft. 4.0

Thiourea mg./ft. 600

EXAMPLE II A coating similar to the coating described in Example I above was prepared, except that 3,6-bis(2-hydroxyethyl)- 2,3,4,5,6,7-hexahydro-1,8-dioxy-3-diazophenanthrene was used as the incorporated black-and-white developer.

This coating had the following structure:

Mg./ft. Incorporated developer 83 Solantine Pink 4BL (CI 25380) 25 Poly-a-methylallylaminoguanidine acetate 66 Silver halide 50 Photographic gelatin 400 Activator B Carboxymethyl cellulose (1%) ml 100 Sodium hydroxide (50%) ml. 4 2-hydroxy-3-aminophenazine g .15 Potassium bromide g .5 Benzotriazole g .05 Sodium chloride g 10.0

EXAMPLE III A three-color multilayer coating corresponding to the following structure was prepared.

Mg./ft. Blue-sensitive silver bromoiodide, mg. of silver 108 Gelatin 310 Poly-a-methylallylaminoguanidine acetate 100 Solantine Yellow RL (CI 29025) 35 Green-sensitive silver bromoiodide (mg. of silver) 108 Gelatin 206 Poly-u-methylallylaminoguanidine acetate 66 Solantine Pink 4BL (CI 25380) 26 Red-sensitive silver bromoiodide (mg. of silver) 108 Gelatin 203 Poly-a-methylallylaminoguanidine acetate 63 Niagara Sky Blue 6B (CI 24410) 26 White pigmented cellulose acetate support.

This coating was then soaked for 3 minutes in a solution of 50 g. of the developer, 4-{oz-[N,N bis(fl hydroxyethyl) amino] methyl}-2-methylhydroquinone dimethyl sulfate in 1 liter of water, after which time the coating was air dried. The coating was then exposed through a 0.3 neutral density step tablet for 3 seconds at 18" with a No. 212 Photoenlarger Lamp and a 2B filter. The exposed coating was then processed by immersion in Activator C (see below) for 40 seconds, and then squeegeed in contact with the acid sheet No. 1 of Example I for 2 minutes. A positive dye image was obtained in the matrix and the silver was removed.

8 Activator C Water g liter 1 Sodium hydroxide (50%) ml 5 2-hydroxy-3-aminophenazine g 1.5 Sodium chloride g Potassium bromide g 5 EXAMPLE IV Example III was repeated using acid sheet No. 2 having a structure as described below, in place of the acid sheet used in Example III. The results were similar to those obtained in Example III above.

Acid Sheet No. 2

The acid sheet No. 2 used above is composed of cellulose acetate film base having a single layer coating thereon of the following composition:

Resin (Amberlite IR12OH) g./ft. 2

Thiourea ..Ing./ft. 900

Polyvinyl alcohol rng./ft. 500

EXAMPLE V A multilayer single-color coating corresponding to the following structure was prepared.

Mg./ft.

White pigmented cellulose acetate support.

This coating was exposed through a .3 neutral density step tablet for 3 seconds at 18" with a No. 212 Photoenlarger Lamp and processed as follows: The exposed coating was squeegeed in-contact for 2 minutes with the acid sheet No. 1 described in Example I, with a .004" spacer, using the following viscous activator solution:

Activator D v Carboxylmethyl cellulose (1%) liter 1 Sodium hydroxide.(50% ml- 16 Sodium chloride g 100 2-hydroxy-3-aminophenazine g 1.6 S-methylbenzotriazole 1% ml.. 60 Methylaminoethanosulfite complex (20% soln.) ml..- 5

A positive dye image was obtained in the coating simultaneously with the removal of the silver.

EXAMPLE VI Example V was repeated but using an acid sheet containing a timing layer (i.e., a layer which increases the diffusion time allowing development to become completed before the pH is shifted to an acid condition). This acid sheet was prepared by overcoating the acid sheet of Example I with a timing compositioncontaining 570 mg./ft. of polyvinyl alcohol and 570 mg./ft. of polyvinyl acetate.

In the developer solution the rnethylaminoethanolsulfite complex of Example V was omitted and'the NaCl was replaced with 100 g. of NaNO A positive dye image of good quality was obtained. All of the silver was removed. The results appeared substantially identical with those of Example V.

EXAMPLE VII The silver halide coating described in Example I was exposed as in Example I and processed by squeegeeing the coating into .contact 'with fan acid sheet No. 3 (structure below) usingviscous activator E, 0.006"thick between the element and the sheet.

9 Acid Sheet- No. 3

pH as mixed was 13.0.

Results similar to those obtained in Example I were obtained.

EXAMPLE VIII A three-color multilayer coating corresponding to the following structure was prepared:

Mg. Blue-sensitive silver chlorobromine emulsion 54 Photographic gelatin 200 Solantine Yellow RL (CI 29025) 35 Poly-a-methylallylaminoguanidine acetate 100 Hydroquinone 4O 1-phenyl-3-pyrazolidone Photographic gelatin 100 Green-sensitive silver-bromoiodide emulsion 54 Photographic gelatin 200 Solantine Pink 4BL (CI 25380) 26 Poly-u-methylallylaminoguanidine acetate 66 Hydroquinone 60 1-phenyl-3-pyrazolidone Photographic gelatin 100 Red-sensitive silver bromoiodide emulsion 54 Photographic gelatin 200 Cyan colored dye described at bottom of page 1 of US. Patent 1,829,673 35 Poly-a-methylallylaminoguanidine acetate 90 Hydroquinone 80 1-pheny1-3-pyrazolidone White pigmented cellulose acetate support.

A sample of the above multilayer film was used to record a picture ,using a camera of the type described in US. Patent 2,543,160, and using an exposure index of ASA 5. The exposed film was then developed by squeegeeing it into contact with an acid sheet No. 3 (of Example VII) at 75 F. for 1.5 minutes using Activator F, with a .008" spacer. After activation, the film was separated from the web, the viscous activator Was squeegeed from the surface of the film which contained a good quality 3-color positive dye image of the subject. All of the silver was removed simultaneously with the formation of the dye image.

10 Activator F Water ml: 500 3amino-2-hydroxyphenazine gms 1.6 Sodium hydroxide gms 28 Sodium sulfite (anhydrous) gms 10 Potassium chloride -gms 50 6-nitrobenzimi-dazole -gms 6 Ascorbic acid gms 6 Dimethylsulfoxide m1s 2 Hydroxyethylcellulose grns 40 Water to (pH 13.2) liter 1 EXAMPLE IX A three-color multilayer coatin was prepared similar to that of Example VIII except that a total of 750 mg/ft of sodium benzene sulfonate was incorporated into a removable cellulose acid phthalate overcoat of said coating. A sample of this film was used to record a picture as described in Example VII. The exposed film was then developed by squeegeeing it into contact with acid sheet No. 3 of Example VII at 75 F. for 1.5 minutes using an activator similar to Activator F of Example VIII with a .008" spacer (except that the strong acid salt, potassium chloride, was not used). After activation the film was separated from the web. The viscous activator and removable overcoat were squeegeed from the surface of the film which contained a good quality three-color image of the subject. All of the silver was removed simultaneously with the formation of the dye image.

This system is not limited to aqueous solutions but is readily adopted to the use of webs coated with succinamide or polyethylene oxide containing the alkali and, optionally, other processing agents. The web may be placed against the exposed photographic element and heated to develop a metallic silver image, thus two webs can be used to proces the photographic dye-bleach element by contacting the element first with a web containing the alkali, and then with a web containing free acid and silver halide complexing agent. Preferably, heat is applied to the first processing web to facilitate development.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

We claim:

1. The process of providing dye images in a photographic element having a support carrying an alkalipermeable layer having in association therewith a bleachable dye, a metallic silver image and a sufiicient quantity of the salt of an acid which, when converted to its free acid form, lowers the pH of said layer to a level at which the dye is bleached imagewise in the presence of a silver complexing agent in the areas of the metallic silver image, said salt of an acid being non-detrimental to the photographic element, which comprises contacting said layer with a processing web having free acid substit-uents which exchange hydrogen ion with the cation of said salt of an acid whereby said salt of an acid is converted to its free acid form and the pH of said layer is reduced to a level at which the dye is bleached imagewise in the presence of said silver complexing agent in the areas of the metallic silver image.

'2. The process of claim 1 wherein the salt employed is the salt of an acid having an ionization constant greater than 10*.

3. The process of claim 1 wherein the salt of an acid employed is selected from the group consisting of the ammonium, substituted ammonium, alkali metal and the alkaline earth chloride, bromides, nitrates, sulfates, sulfonates, phosphates and phosphonates, and the processing web comprises a support having coated thereon an alkali-permeable layer containing a free acid selected '1 1 from the group consisting of a strongly acidic polymer, ballasted sulfonic acid and a ballasted phosphonic acid.

4. The process of claim 3, wherein said salt of an acid and said free acid, respectively, are present in sufiicient concentration in said layer and said processing web so that when said processing web is pressed against said layer, the pH of the layer is lowered to less than about 2.0 by exchange of the hydrogen ion of said free acid and the cation of said salt of an acid.

5. The method of producing dye images in a photographic element comprising a support having coated thereon a gelatin silver halide emulsion containing a developed silver image, a non-diffusible bleached dye and potassium chloride which comprises contacting said element with an acidic processing web comprising a support having coated thereon alpha-sulfostearic acid in polyvinyl alcohol, said potassium chloride and said alpha-sulfostearic acid, respectively, being present in said emulsion and said processing web in concentrations sufiicient to lower the pH of said layer to about 1.0 when said processing web is pressed against said emulsion, thereby causing exchange of the hydrogen ion of said alpha-sulfostearic acid with the cation of said potassium chloride, and bleaching said dye imagewise in the presence of a silver complexing agent at a pH of about 1.0 in the areas of said metallic silver, said bleaching being catalyzed with 2-hydroxy-3-aminophenazine.

6. In the method of providing dye images in an imagewise exposed photographic element having a support coated with an alkali-permeable colloid layer containing silver halide and having in association therewith a nondifiusible bleachable dye, which includes contacting said layer in the presence of a silver halide developer with an alkaline processing solution to raise the pH of the emulsion to a level at which development of silver halide to metallic silver takes place, reducing the pH to a level at which bleaching of the metallic silver to silver ion takes place, complexing the silver ion with a silver complexing agent, and bleaching the dye imagewise in the presence of the silver complexing agent in the areas of metallic silver image, the improvement comprising:

(a) introducing into said layer at least a sufficient quantity of the salt of an acid which, when converted to its free acid form, lowers the pH of the layer to a level at which the dye is bleached imagewise in the presence of the silver complexing agent in areas of the metallic silver, said salt of an acid being non-detrimental to the photographic element; and

(b) contacting said layer with a processing web having free acid substituents which exchange hydrogen ion with the cation of said salt of an acid, thereby converting a sufiicient amount of said salt of an acid to its free acid form to lower the pH of said layer to a level at which the dye is bleached.

7. The method of claim 6, wherein the salt employed is the salt of an acid having an ionization constant greater than l 8. The process of claim 6, wherein the salt of an acid employed is selected from the group consisting of the ammonium, substituted ammonium, alkali metal and the alkaline earth chlorides, bromides, nitrates, sulfates, sulfonates, phosphates, and phosphonates, and the processing web comprises a support having coated thereon an alkalipermeable layer containing a free acid selected from the group consisting of a strongly acidic polymer, a ballasted sulfonic acid and a ballasted phosphonic acid.

9. The process of claim 6, wherein said salt of an acid and said free acid, respectively, are present in sufficient concentrations in said layer and said processing web so that when said processing web is pressed against said layer, the pH of the layer is lowered to less than about 2.0 by exchange of the hydrogen ion of said free acid with the cation of said salt of an acid.

10. An integral three-part photographic element useful in the silver dye bleach process:

Part 1 comprising a support having thereon an alkalipermeable layer containing light sensitive silver halide, said layer having in association therewith a bleachable dye;

Part 2 comprising a pressure rupturable pod containing an alkaline processing solution which, when contacted with said layer of Part 1, raises the pH thereof to a level at which silver halide is developed imagewise to metallic silver when a silver halide developer is present; and

Part 3 comprising a web having free acid substituents;

Parts 1 and 3 during processing being in superimposed relation with said layer facing said web, and Part 2 being positioned between Parts 1 and 3;

At least one of said Parts 1 and 2 containing a silver halide developer; and

At least one of said Parts 1 and 2 containing a sufficient quantity of the salt of an acid which, when converted to its free acid form, lowers the pH of said layer of Part 1 to a level at which the dye is bleached imagewise in the presence of a silver complexing agent in areas where metallic silver is present, said free acid substituents in said web being capable of converting at least a sufficient amount of said salt of an acid to its free acid form whereby the pH of said layer of Part 1 is reduced to a level at which said dye of Part 1 is bleached imagewise in the areas of the metallic silver image, at least one of Parts 2 and 3 containing a silver complexing agent, and at least one of Parts 1, 2 and 3 containing a dye bleach catalyst.

11. The photographic element of claim 10, wherein the salt employed is the salt of an acid having an ionization constant greater than l0- 12. The photographic element of claim 10, wherein the salt of an acid employed is selected from the group consisting of the ammonium, substituted ammonium, alkali metal and the alkaline earth chlorides, bromides, nitrates, sulfates, sulfonates, phosphates and phosphonates, and the processing web comprises a support having coated thereon an alkali-permeable layer containing a free acid selected from the group consisting of a strongly acidic polymer, a ballasted sulfonic acid and a ballasted phosphonic acid.

13. The photographic element of claim 10, wherein said salt of an acid and said free acid, respectively, are present in sufiicient concentrations in said layer and said processing web so that when said processing web is pressed against said layer, the pH of the layer is lowered to less than about 2.0 by exchange of the hydrogen ion of said free acid with the cation of said salt of an acid.

14. In the method of providing multicolor dye images in an imagewise exposed photographic element comprising a support having coated thereon at least three separate alkali-permeable colloid layers containing, respectively, blue-sensitive silver halide and having in association therewith a non-difitusible bleachable yellow dye, green-sensitive silver halide having in association therewith a non-dilfusible bleachable magenta dye and a redsensitive silver halide having in association therewith a non-ditfusible bleachable cyan dye, which includes contacting said layers in the presence of a silver halide developer with an alkaline processing solution to raise the pH of the emulsion to a level at which development of silver halide to metallic silver takes place, reducing the pH to a level at which bleaching of the metallic silver to silver ion takes place, complexing the silver ion with a silver complexing agent, and bleaching the dye imagewise in the presence of the silver complexing agent in the areas of metallic silver image, the improvement comprising:

(a) introducing into said layers at least a sufiicient quantity of the salt of an acid which, when con- 13 verted to its free acid form, lowers the pH of the layers to a level at which the dye is bleached imagewise in the presence of the silver complexing agent in areas of the metallic silver, said salt of an acid being non-detrimental to the photographic element; and

(b) contacting said layers with a processing web having free acid substituents which exchange hydrogen ion with the cation of said salt of an acid, thereby converting a sufficient amount of said salt of an acid to its free acid form to lower the pH of said layers to a level at which the dye is bleached.

15. The method of claim 14, wherein the salt employed is the salt of an acid having an ionization constant greater than 10- 16. The process of claim 14, wherein the salt of an acid employed is selected from the group consisting of the ammonium, substituted ammonium, alkali metal and the alkaline earth chlorides, bromides, nitrates, sulfates,

sulfonates, phosphates and phosphonates, and the processing web comprises a support having coated thereon an alkali-permeable layer containing a free acid selected from the group consisting of a strongly acidic polymer, a ballasted sulfonic acid and a ballasted phosphonic acid.

17. The process of claim 14, wherein said salt of an acid and said free acid, respectively, are present in sufficient concentrations in said layers and said processing web so that when said processing web is pressed against said layers, the pH of the layers is lowered to less than about 2.0 by exchange of the hydrogen ion of said free acid with the cation of said salt of an acid.

No references cited.

NORMAN G. TORCHIN, Primary Examiner.

A. T. SUROPICO, Assistant Examiner.

UNITED STATESIATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,414,411 December 3, 1968 Stephen Michel et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 10, line 72, "chloride" should read'' chlorides Column 11, line 13, "bleached" should read bleachable Signed and sealed'this 10th day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHIIYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr. Attesting Officer 

6. IN THE METHOD OF PROVIDING DYE IMAGES IN AN IMAGEWISE EXPOSED PHOTOGRAPHIC ELEMENT HAVING A SUPPORT COATED WITH AN ALKALI-PERMEABLE COLLOID LAYER CONTAINING SILVER HALIDE AND HAVING IN ASSOCIATION THEREWITH A NONDIFFUSIBLE BLEACHABLE DYE, WHICH INCLUDES CONTACTING SAID LAYER IN THE PRESENCE OF A SILVER HALIDE DEVELOPER WITH AN ALKALINE PROCESSING SOLUTION TO RAISE THE PH OF THE EMULSION TO A LEVEL AT WHICH DEVELOPMENT OF SILVER HALIDE TO METALLIC SILVER TAKES PLACE, REDUCING THE PH TO A LEVEL AT WHICH BLEACHING OF THE METALLIC SILVER TO SILVER ION TAKES PLACE, COMPLEXING THE SILVER ION WITH A SILVER COMPLEXING AGENT, AND BLEACHING THE DYE IMAGEWISE IN THE PRESENCE OF THE SILVER COMPLEXING AGENT IN THE AREAS OF METALLIC SILVER IMAGE, THE IMPROVEMENT COMPRISING: (A) INTRODUCING INTO SAID LAYER AT LEAST A SUFFICIENT QUANTITY OF THE SALT OF AN ACID WHICH, WHEN CONVERTED TO ITS FREE ACID FORM, LOWERS THE PH OF THE LAYER TO A LEVEL AT WHICH THE DYE IS BLEACHED IMAGEWISE IN THE PRESENCE OF THE SILVER COMPLEXING AGENT IN AREAS OF THE METALLIC SILVER, SAID SALT OF AN ACID BEING NON-DETRIMENTAL TO THE PHOTOGRAPHIC ELEMENT; AND (B) CONTACTING SAID LAYER WITH A PROCESSING WEB HAVING FREE ACID SUBSTITUENTS WHICH EXCHANGE HYDROGEN ION WITH THE CATION OF SAID SALT OF AN ACID, THEREBY CONVERTING A SUFFICIENT AMOUNT OF SAID SALT OF AN ACID TO ITS FREE ACID FORM TO LOWER THE PH OF SAID LAYER TO A LEVEL AT WHICH THE DYE IS BLEACHED.
 10. AN INTEGRAL THREE-PART PHOTOGRAPHIC ELEMENT USEFUL IN THE SILVER DYE BLEACH PROCESS: PART 1 COMPRISING A SUPPORT HAVING THEREON AN ALKALIPERMEABLE LAYER CONTAINING LIGHT SENSITIVE SILVER HALIDE, SAID LAYER HAVING IN ASSOCIATION THEREWITH A BLEACHABLE DYE; PART 2 COMPRISING A PRESSURE RUPTURABLE POD CONTAINING AN ALKALINE PROCESSING SOLUTION WHICH, WHEN CONTACTED WITH SAID LAYER OF PART 1, RAISES THE PH THEREOF TO A LEVEL AT WHICH SILVER HALIDE IS DEVELOPED IMAGEWISE TO METALLIC SILVER WHEN A SILVER HALIDE DEVELOPER IS PRESENT; AND PART 3 COMPRISING A WEB HAVING FREE ACID SUBSTITUENTS; PARTS 1 AND 3 DURING PROCESSING BEING IN SUPERIMPOSED RELATION WITH SAID LAYER FACING SAID WEB, AND PART 2 BEING POSITIONED BETWEEN PARTS 1 AND 3; AT LEAST ONE OF SAID PARTS 1 AND 2 CONTAINING A SILVER HALIDE DEVELOPER; AND AT LEAST ONE OF SAID PARTS 1 AND 2 CONTAINING A SUFFICIENT QUANTITY OF THE SALT OF AN ACID WHICH, WHEN CONVERTED TO ITS FREE ACID FORM, LOWERS THE PH OF SAID LAYER OF PART 1 TO A LEVEL AT WHICH THE DYE IS BLEACHED IMAGEWISE IN THE PRESENCE OF A SILVER COMPLEXING AGENT IN AREAS WHERE METALLIC SALT IS PRESENT, SAID FREE ACID SUBSTITUENTS IN SAID WEB BEING CAPABLE OF CONVERTING AT LEAST A SUFFICIENT AMOUNT OF SAID SALT OF AN ACID TO ITS FREE ACID FORM WHEREBY THE PH OF SAID LAYER OF PART 1 IS REDUCED TO A LEVEL AT WHICH SAID DYE OF PART 1 IS BLEACHED IMAGEWISE IN THE AREAS OF THE METALLIC SILVER IMAGE, AT LEAST ONE OF PARTS 2 AND 3 CONTAINING A SILVER COMPLEXING AGENT, AND AT LEAST ONE OF PARTS 1, 2 AND 3 CONTAINING A DYE BLEACH CATALYST. 